Flat planner pressure transducer

ABSTRACT

There is disclosed flat planar pressure transducer which comprises a planar insulative substrate of a rectangular configuration. Disposed on the substrate is an array of conductive areas which extend from a contact terminal area of said substrate to an end of the substrate. There is a leadless sensor module positioned at said contact terminal area, with the contacts of said leadless sensor contacting contact terminals of said contact terminal area. The leadless sensor is enclosed by an enclosure which is coupled to the substrate and surrounds the sensor. The enclosure has a screen positioned on the top surface to prevent particles from entering or damaging the leadless sensor. The above-noted structure forms a very flat, compact pressure transducer which can be utilized in lieu of flex circuit type devices and provides greater mechanical stability as well as a more accurate output.

FIELD OF THE INVENTION

This invention relates to pressure transducers and more particularly toa flat pack planar transducer structure.

BACKGROUND OF THE INVENTION

As one can ascertain, pressure transducers are used in many applicationsfor measuring pressure in various environments. In any event, in certainapplications it is extremely desirable that the pressure transducershave a very low profile and essentially have a configuration where itcan be mounted on curved or other surfaces. In order to do this thetransducer has to be relatively small and relatively flat. Suchtransducers exist in a prior art and used what is designated as flexiblecircuits. These flexible circuits essentially consist of metalized leadsplaced on a suitable plastic substrate. In this manner the substratealso contains a pressure transducer whereby the substrate can bend orcurve and be placed on a curved surface creating a close contact andhaving a low profile. When employing such flex circuits, it has beendetermined that they are not stable as the plastic can changedrastically according to temperature and so on. Therefore, these devicesare not mechanically stable and present problems. It is therefore adesire of the present invention to provide an improved flat planartransducer structure which is very thin and which has increasedstability and because of the nature of the structure, can be mounted onvarious surfaces, included arcuate surfaces without affecting theprofile of the surface.

SUMMARY OF THE INVENTION

A pressure transducer, comprising: a planar insulative substrate member,an array of conductive areas extending from a contract terminal area ofsaid substrate to an end of said substrate, where said areas at saidcontact terminal form conductive contacts, with each contact extendingvia an elongated path to said end of said substrate, a leadless sensormodule having contacts, said sensor positioned at said contact terminalarea of said substrate with the contacts of said leadless sensorcontacting an associated conductive contract on said substrate, anenclosure coupled to said substrate and positioned to enclose saidsensor.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective plan view of a transducer assembly according tothis invention.

FIG. 2 is a exploded view depicting the parts utilized in the assemblyof FIG. 1.

FIG. 3 is a cross-sectional view of the assembly of FIG. 1 for a clearerunderstanding of the invention.

FIG. 4 is a top plan view of the planar pressure transducer according tothis invention.

FIG. 5 is a cross-sectional view of the transducer assembly.

FIG. 6 is an exploded view showing the various parts utilized in aleadless sensor arrangement employed with the transducer according tothis invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is shown a flat planar transducer assembly 10according to this invention. A planar insulative member 11, which can beconstructed from a suitable glass, such as a Pyrex glass and so on, actsas a mounting substrate for the planar transducer. On the glasssubstrate 11 is formed a layer of chromium by either sputtering orevaporating. The glass substrate 11 is covered with a substance such asphoto-resist. The photo-resist acts as a mask for etching the chromiumby any convenient means. The area in which the chromium is removed willform the channels on the glass substrate. Using the remaining chromiumas a mask the glass substrate is etched forming a series of grooves. Theglass substrate is etched using a mixture of hydrofluoric and nitricacid to a desired depth. After the glass pattern is etched to asufficient depth the chromium is stripped. The glass is then coveredwith a layer of titanium and platinum. Then a second photo-resist maskis used to cover the glass substrate in such a way so that the titaniumand platinum is etched away except in the grooves previously defined.Therefore, a series of conductive channels such as 12, 15 and 16 areformed. These conductive channels 12, 15 and 16 are all insulated onefrom another due to the glass substrate.

Referring to FIG. 2, there is shown the exact nature of the conductivechannels such as 12, 15 and 16. And as seen, channel 12 emanates in acontact area 21, channel 16 in the contact area 22 as do the otherchannels. These contact areas are positioned on the glass substrate 11so that direct contact can be made to a leadless sensor device 20. Theleadless sensor device 20 is a semiconductor device which essentially isdevoid of leads but has suitable contacts. These contacts make contactwith the contact areas 21 and 22 on the glass substrate and thereforeenable contact to be made to the leadless semiconductor sensor 20. Theleadless semiconductor sensor is secured to the glass substrate 11 bymeans of a glass bond or a glass-metal frit seal. Sealing of suchdevices are well known and glass-metal frits utilized for sealingsemiconductor sensors to a glass substrate is also well known. In regardto the semiconductor sensor, more detail will be explained subsequently.In any event, the structure 20 is designated as a leadless semiconductordevice. Such devices are manufactured by Kulite Semiconductor Products,Inc., the assignee herein. For examples of such devices see U.S. Pat.No. 5,973,590 issued on Oct. 26, 1999 to A. D. Kurtz, et al., aninventor herein. The patent is assigned to Kulite SemiconductorProducts, Inc., the assignee herein and is entitled Ultra Thin SurfaceMount Wafer Sensor Structures and Methods for Fabricating Same. See alsoU.S. Pat. No. 6,210,989 issued on Apr. 3, 2001 to A. D. Kurtz, et al.,and assigned to the assignee herein. That patent is entitled Ultra ThinSurface Mount Wafer Sensor Structures and Methods for Fabricating Same.See also U.S. Pat. No. 6,272,929 issued Aug. 14, 2001 to A. D. Kurtz, etal., and entitled High Pressure Piezoresistive Transducer Suitable ForUse In Hostile Environments. In any event, as indicated, the transducerassembly 20 is the assembly depicted in the above-noted patents, all ofwhich are incorporated herein in their entirety. The sensor 20 istherefore a leadless sensor, is extremely thin and compact. As seen,there is a screen holder or a circular housing 19. The housing 19 has aperipheral flange 32 into which a screen member 18 is inserted. Screenmember 18, as one can ascertain, has a plurality of apertures as 34 and35. These apertures prevent particles from entering the housing and thusserves as a screen. As indicated, the pressure transducer can beemployed in hostile environments. Such transducers may be utilized inwind tunnel applications or other uses to measure pressure and so on.Such wind tunnels or other hostile environments may carry relativelylarge particles which can impinge upon the semiconductor diaphragm anddamage the same. Therefore, the screen, as shown 18, operates to preventsuch particles from impinging on or otherwise damaging the transducer 20assembly.

As seen in FIG. 1 and FIG. 2, the leads as 13, 14, 17 and 23 aredirectly connected to the terminals areas as 12, 15 and 16. This can bedone by typical solder or other conventional bonding techniques.

Referring to FIG. 4 there is shown a top-plan view of the sensorconfiguration depicted in FIG. 10. The same reference numerals have beenutilized to designate the same parts. As seen, the substrate 11 is glassand has etched therein channels to accommodate the conductive metalareas as 12 and 15. The screen holder 19, as well as the screen 18, aredepicted in FIG. 4.

FIG. 5 is a cross-sectional view showing the sensor 20 configurationwhich is secured to the glass substrate 11 by means of a glass fritwhich can operate as a paste and which enables one to secure thesemiconductor 20 to the substrate 11. In this manner, contact betweenthe semiconductor contacts and the contact areas on the substrate suchas areas 21 and 22 are facilitated.

Referring to FIG. 6 there is shown a detailed depiction in exploded viewof the leadless semiconductor structure 20 employed with the presentinvention. As one can ascertain, FIG. 6 is FIG. 7 of U.S. Pat. No.6,210,989 as well as FIG. 7 of U.S. Pat. No. 5,973,590. While thepatents have a detailed description of the structure depicted in FIG. 7and while the above-noted patents are incorporated herein, a shortdescription of the Figure will be given. As can be seen from FIG. 6,there is a semiconductor wafer 40, which wafer contains a piezoresistivearray 41, which array is normally connected in a Wheatstone bridgearrangement. The array is coupled to contact areas 42, which contactareas enable contact to the semiconductor piezoresistor 41. There isshown a glass wafer 72 which is secured to the silicon wafer plusanother glass contact wafer 73 which is a ceramic or glass and whichenables contact to be made to the contact areas of the silicon sensor40. The member 43 has apertures as 75 and 76 which can be filled with aconductive material to enable contact to be made with the contact areason the silicon sensor wafer 40. This designation, as indicated, is aleadless semiconductor and which basically contains a semiconductordiaphragm having an oxide layer where one then fusion bonds P+ sensorelements to the oxide layer and then one fusion bonds the fingerelements to the oxide layer and fabricates the device. As indicated, theconstruction of such devices is clearly depicted in the above-notedpatents whereby one can determine the exact nature of the leadlesssemiconductor sensor 20 utilized in the planar transducer according tothis invention.

One will ascertain, again referring to FIG. 5, that the final packagecan be coated or covered with a typical protective layer of epoxy or apotting compound and therefore fully protected from the environment.Thus, as indicated above, there is shown a flat planar pressuretransducer which can be utilized in lieu of flex circuits and whichprovides a very thin and stable circuit. The typical dimensions of theglass substrate 11, would be approximately 0.125 inches in width and0.225 inches in length. The thickness of the glass substrate 11 would beapproximately 0.02 inches. The screen holder member 19 has a outerdiameter of 0.125 inches with an inner diameter of 0.115 inches and athickness of approximately 0.038 inches. In this manner as one canascertain from the above-noted dimensions, the device is extremely smalland can be positioned on various surfaces without disturbing the profileof the surface. Therefore, such devices as indicated can be used tomeasure pressure in wind tunnels and various other environments wherethere is a necessity to measure pressure with a minimal disturbance tothe pressure profile. Thus, it will become apparent to one skilled inthe art, that there are alternate embodiments and structures which maybe perceived from reading the above-noted specification, all of whichare deemed to be encompassed within the scope of the claims appendedhereto.

1. A pressure transducer, comprising: a planar insulative substratemember, an array of conductive areas extending from a contract terminalarea of said substrate to an end of said substrate, where said areas atsaid contact terminal area form conductive contacts, with each contactextending via an elongated path to said end of said substrate, aleadless sensor module having contacts, said sensor positioned at saidcontact terminal area of said substrate with the contacts of saidleadless sensor contacting an associated conductive contract on saidsubstrate, an enclosure coupled to said substrate and positioned toenclose said sensor.
 2. The pressure transducer according to claim 1wherein said insulative substrate is a glass substrate.
 3. The pressuretransducer according to claim 2, wherein said glass is pyrex.
 4. Thepressure transducer according to claim 1 wherein said array ofconductive areas are channels formed in said substrate wherein eachchannel has a metal deposited therein to form a conductive area.
 5. Thepressure transducer according to claim 2 wherein said glass substrate isa rectangular substrate having a length greater than the width.
 6. Thepressure transducer according to claim 5 wherein said conductive areaextends along the length of said substrate.
 7. The pressure transduceraccording to claim 1 wherein said enclosure is a circular enclosurehaving an opened top and bottom, with said bottom secured to saidsubstrate to encircle said leadless sensor.
 8. The pressure transduceraccording to claim 7 further comprising a screen member having aplurality of apertures on a surface, said screen member secured to saidenclosure to cover said opened top.
 9. The pressure transducer accordingto claim 1 wherein said leadless sensor is a semiconductor sensor havingan array of piezoresistive elements.
 10. The pressure transduceraccording to claim 9 wherein said piezoresistive elements are P+semiconductor elements.
 11. The pressure transducer according to claim10 wherein said array of piezoresistive elements form a Wheatstonebridge.
 12. The pressure transducer according to claim 2 wherein saidleadless sensor is secured to said substrate by a glass bond.
 13. Thepressure transducer according to claim 9 wherein said semiconductor issilicon.
 14. The pressure transducer according to claim 13 wherein saidsilicon semiconductor has a silicon diaphragm which deflects uponapplication of a force thereto and with said array of piezoresistiveelements positioned on said diaphragm.
 15. A pressure transducer,comprising: a planar insulative substrate member having a plurality ofcontact channels formed on a surface of said insulative member, saidcontact channels extending from a contact area array on said insulativesubstrate to an end of said substrate, each channel associated with aseparate contact area wherein said contact area form said array, aconductive material deposited in said channels and said contact areas toform a plurality of conductive paths, each path having an associatedcontact area and a conductive channel, a leadless sensor module havingcontacts, said sensor positioned at said contact area array of saidsubstrate with said contacts of said sensor contacting an associatedcontact area, to enable connections to be made to said sensor module viasaid conductive channels, an enclosure coupled to said substrate andpositioned to enclose said sensor.
 16. The pressure transducer accordingto claim 15 further comprising: a plurality of wires, each wire coupledto an associated channel for enabling contact with said sensor module.17. The pressure transducer according to claim 15 wherein saidinsulative substrate is glass.
 18. The pressure transducer according toclaim 17 wherein said sensor module is secured to said substrate by aglass bond.
 19. The pressure transducer according to claim 2 whereinsaid channels and contact areas are etched in to said glass substrate.20. The pressure transducer according to claim 19 wherein said channelsand contact areas are filled with a sputtered metal.